1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Show that f'(a) = g(a) ?

  1. May 6, 2012 #1
    1. The problem statement, all variables and given/known data

    1C-2 Let f(x) = (x - a)g(x). Use the definition of the derivative to calculate that f'(a) = g(a), assuming that g is continuous

    2. Relevant equations

    3. The attempt at a solution

    I just started a self study of calculus using Khan and MIT OpenCourse. I am bit stuck, or maybe confused, with this exercise from MIT 18.01

    The definition for the derivative is

    I can replace f(x) with (x-a)g(x), but I don't know what to do with f(a). In the given solution f(a) somehow becomes 0, but I can't see how.

    The given solution:

    Any help is much appreciated.

    Attached Files:

  2. jcsd
  3. May 6, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    f(a) = (a-a)g(a) = 0.
  4. May 7, 2012 #3
    ah - of course. Thank you very much
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook